           $( function () {
            var show_num = [];
            draw( show_num );
            $( "#canvas" ).on( 'click', function () {
                draw( show_num );
            } )
            $( "#input_password" ).on( 'blur', function () {
                var val = $( "#input_password" ).val().toLowerCase();
                var num = show_num.join( "" );
                if ( val == '' ) {
                    $( ".pwd_null" ).addClass( "pwd_show" ).siblings().removeClass( "pwd_show" );
                    $( ".btn-pwd" ).attr( "disabled", true )
                    return false;
                } else if ( val == num ) {
                    $( ".pwd_true" ).addClass( "pwd_show" ).siblings().removeClass( "pwd_show" );
                    $( ".btn-pwd" ).attr( "disabled", false );
                    $( ".input-val" ).val( '' );
                    return true;
                } else {
                    $( ".pwd_false" ).addClass( "pwd_show" ).siblings().removeClass( "pwd_show" );
                    $( ".btn-pwd" ).attr( "disabled", true )
                    $( ".input-val" ).val( '' );
                    // draw(show_num);
                    return false;
                }
            } )
        } )
    //生成并渲染出验证码图形
    function draw( show_num ) {
        var canvas_width = $( '#canvas' ).width();
        var canvas_height = $( '#canvas' ).height();
        var canvas = document.getElementById( "canvas" ); //获取到canvas的对象，演员
        var context = canvas.getContext( "2d" ); //获取到canvas画图的环境，演员表演的舞台
        canvas.width = canvas_width;
        canvas.height = canvas_height;
        var sCode = "a,b,c,d,e,f,g,h,i,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,W,X,Y,Z,1,2,3,4,5,6,7,8,9,0";
        var aCode = sCode.split( "," );
        var aLength = aCode.length; //获取到数组的长度
        for ( var i = 0; i < 4; i++ ) { //这里的for循环可以控制验证码位数（如果想显示6位数，4改成6即可）
            var j = Math.floor( Math.random() * aLength ); //获取到随机的索引值
            // var deg = Math.random() * 30 * Math.PI / 180;//产生0~30之间的随机弧度
            var deg = Math.random() - 0.5; //产生一个随机弧度
            var txt = aCode[ j ]; //得到随机的一个内容
            show_num[ i ] = txt.toLowerCase();
            var x = 10 + i * 20; //文字在canvas上的x坐标
            var y = 20 + Math.random() * 8; //文字在canvas上的y坐标
            context.font = "bold 23px 微软雅黑";
            context.translate( x, y );
            context.rotate( deg );
            context.fillStyle = randomColor();
            context.fillText( txt, 0, 0 );
            context.rotate( -deg );
            context.translate( -x, -y );
        }
        for ( var i = 0; i <= 5; i++ ) { //验证码上显示线条
            context.strokeStyle = randomColor();
            context.beginPath();
            context.moveTo( Math.random() * canvas_width, Math.random() * canvas_height );
            context.lineTo( Math.random() * canvas_width, Math.random() * canvas_height );
            context.stroke();
        }
        for ( var i = 0; i <= 30; i++ ) { //验证码上显示小点
            context.strokeStyle = randomColor();
            context.beginPath();
            var x = Math.random() * canvas_width;
            var y = Math.random() * canvas_height;
            context.moveTo( x, y );
            context.lineTo( x + 1, y + 1 );
            context.stroke();
        }
    }
    //得到随机的颜色值
    function randomColor() {
        var r = Math.floor( Math.random() * 256 );
        var g = Math.floor( Math.random() * 256 );
        var b = Math.floor( Math.random() * 256 );
        return "rgb(" + r + "," + g + "," + b + ")";
    } 
